1. Technical Field
The present disclosure relates to an alkylation process for the production of an alkylaromatic from an olefin and an aromatic, and particularly to the production of ethylbenzene from ethylene and benzene.
2. Background of the Art
Various processes for the production of alkylbenzene by the alkylation of benzene with an olefin are known in the art. Among the most common olefins used are ethylene and propylene. The alkylation of benzene with ethylene produces ethylbenzene. The alkylation of benzene with propylene produces cumene.
Ethylbenzene is an important chemical used mostly as a precursor for the production of styrene, which is subsequently polymerized to produce polystyrene. Various methods are known for the production of ethylbenzene. Typically, benzene and ethylene are combined in an alkylation reaction in the presence of a suitable catalyst. Various alkylation catalysts are known, and commonly used catalysts include Friedel-Crafts catalysts such as aluminum or boron halides, and various zeolites.
The reaction produces, in addition to ethylbenzene, a byproduct containing polyethylbenzenes (“PEB”) such as diethylbenzene, triethylbenzene and tetraethylbenzene. The polyethylbenzenes are undesirable and are usually recycled to a transalkylation reactor for conversion to ethylbenzene by reaction with benzene.
Ethylbenzene has been produced in a process wherein the alkylation reaction was performed by catalytic distillation. The zeolite catalyst is contained in specially packaged bales, and the alkylation reaction is conducted in mixed vapor-liquid phase.
U.S. Pat. No. 5,003,119 to Sardina et al., which is incorporated by reference herein, discloses a process for the manufacture of alkylbenzenes, such as ethylbenzene and cumene, wherein a feed of fresh and recycle benzene and fresh olefin are reacted in the presence of an alkylation catalyst in an alkylator having at least two reaction stages wherein each stage is adiabatic. Essentially all of the olefin is completely reacted in each stage of the alkylator. Fresh olefin is fed into each stage of the alkylator.
Up to now, for a dilute ethylene feed, 99% of the ethylene conversion has been achieved in the alkylator. This level of conversion requires a large amount of catalyst. The vent gas from the alkylator is sent to a vent absorber where the benzene is absorbed in a hydrocarbon stream (e.g., polyethylbenzenes). The ethylene contained in the vent gas was ultimately lost. It would be advantageous to have a substantially complete conversion of ethylene with a reduced overall amount of required catalyst.